This application claims the priority of German Patent Applications, Serial Nos. 100 59 862.5, filed Nov. 30, 2000, and 101 52 484.6, filed Oct. 24, 2001, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
The present invention relates, in general, to a clutch release bearing for use in a clutch operator, and more particular to a sealing arrangement for use in a clutch release bearing.
Various approaches are known to seal a clutch release bearing in order to prevent e.g. ingress of dirt and moisture into the interior of the clutch release bearing and escape of lubricant out of the clutch release bearing. German Pat. Publication DE 195 03 217 A1 describes a clutch release bearing for release of a separating clutch, including a torsionally rigid outer bearing ring, a revolving inner bearing ring, which is connected via a spring element to a separating clutch disposed between an internal combustion engine and a gearbox, and rolling elements, which are received in a cage and guided between the bearing rings. Seals are provided on both sides of the clutch release bearing at a distance to the rolling elements. A first sealing arrangement is securely fixed to the outer bearing ring and includes two spread-apart sealing lips which are supported by a cylindrical portion of the revolving inner bearing ring. A second sealing arrangement is secured to the housing and has a sealing lip resting against the revolving inner bearing ring. As the sealing lips of the sealing arrangements are all in sliding contact with the inner bearing ring, friction is increased, resulting in a heat-up of the clutch release bearing so that lubricant is subject to greater stress and the clutch release bearing is prone to fail prematurely. In other words, the service life is shortened. Seals for a clutch release bearing of this type are therefore unsuitable for many applications. In particular, there is a danger that the engagement disc of the, separating clutch causes swirling rubbed-off parts in the clutch housing, which accommodates the clutch release bearing, to migrate past the sealing lip into the clutch release bearing.
It would therefore be desirable and advantageous to provide an improved clutch release bearing which obviates prior art shortcomings and which realizes an enhanced sealing action, while still being simple in construction.
According to one aspect of the present invention, a clutch release bearing includes a housing, an outer first bearing ring having a skirt for fixed rotative securement of the first bearing ring to the housing, a revolving inner second bearing ring connected to the separating clutch via a spring element, a plurality of rolling elements guided between the first and second bearing rings, and sealing means provided on both sides of the rolling elements at a distance thereto, wherein the sealing means includes a sealing arrangement securely fixed to the first bearing ring and comprised of at least two components to establish two sealing zones for sealing an annular gap between the first and second bearing rings, wherein the second bearing ring and the sealing arrangement interact in such a way that a desired installation position of the sealing arrangement is automatically established as the second bearing ring is installed.
The present invention resolves prior art problems by providing a sealing arrangement which is made of at least two components to thereby realize two sealing zones. In this way, the annular gap between the inner and outer bearing rings of the clutch release bearing is effectively sealed. Moreover, the sealing arrangement according to the present invention is so constructed as to automatically occupy the desired sealing disposition, when the revolving bearing ring is installed.
A clutch release bearing according to the present invention incorporating a sealing arrangement in this manner ensures an effective sealing action, even when a motor vehicle is operated under extreme situations, for example an all-terrain vehicle during off-road use. Also, driving through water or exposure to dust will not adversely affect the effectiveness of the sealing arrangement to prevent ingress of foreign particles of any type into the clutch release bearing. Suitably, the sealing arrangement is so constructed as to avoid an inadmissible temperature increase in the sealing zones during the break-in phase or during normal operation. Through proper material selection, wear of the sealing arrangement and thus of the clutch release bearing and the clutch operator can be minimized to ensure an extended service life.
As the clutch release bearing is assembled, the sealing arrangement according to the present invention is able to automatically assume a desired disposition, when the revolving bearing ring is installed. The sealing arrangement occupies the optimum disposition during installation regardless of manufacturing tolerances of individual components of the clutch release bearing that directly interact with the sealing arrangement. In this way, the sealing arrangement is prevented from being loaded in axial direction so that wear is reduced and less heat develops, while at the same time the formation of an excessive sealing gap is precluded to maintain a sufficient sealing quality.
According to another feature of the present invention, the sealing arrangement may include a sealing disc which automatically assumes a defined disposition as the second bearing ring is installed. At the same time, a smallest possible sealing gap can be established, regardless of component tolerances or manufacturing tolerances. This can be realized through suitable configuration of the sealing arrangement and/or through material selection so as to ensure a sealing gap of intentionally slightly greater dimension after a break-in phase, without adversely affecting the sealing quality hereby.
According to another feature of the present invention, the sealing arrangement may include a seal carrier which is securely fixed to the first bearing ring and has a first carrier portion extending at a clearance to the revolving second bearing ring to define an annular gap therebetween for providing a first sealing zone. The seal carrier may include a sealing disc which, is placed at an end surface of the revolving second bearing ring for establishing) the second sealing zone. The two-stage sealing action is so constructed that the first sealing stage of the clutch release bearing protects against ingress of greater particles, while the following second sealing stage provides an effective sealing action against ingress of small or smallest particles such as dust and liquids and prevents an escape of lubricant.
The sealing disc provided for forming the second sealing zone is placed in an installation space which is defined between the end surface of the revolving bearing ring and a radial portion of the seal carrier. Through appropriate material selection of the sealing disc, it is possible to establish after the break-in phase a defined smallest possible sealing gap between the end surface of the revolving bearing ring and the sealing disc. The present invention also includes the provision a sealing disc which is supported on the side facing away from the end surface of the revolving bearing ring by a spring washer or spring element. Hereby, the seal carrier is so configured as to leave an axial clearance between the spring element and the radial portion of the seal carrier. The spring washer or spring element is intended to properly position the sealing disc on a cylindrical portion of the seal carrier, when the revolving bearing ring is installed, without impact on the installed disposition of the seal carrier, so as to establish an optimum position of the sealing disc upon the end surface of the revolving bearing ring.
According to another feature of the present invention, the seal carrier has a free end provided with a radially inwardly directed collar, which is partially or completely wrapped around, to realize a stiffening of the seal carrier. In this way, the stiffness is enhanced and a sealing action is ensured by the defined cylindrical portion of the seal carrier, even after installation of the revolving inner bearing ring.
According to another feature of the present invention, the cylindrical portion of the seal carrier is configured to span over the entire axial length of the revolving bearing ring to thereby extend the annular gap between the inner contour of the revolving bearing ring and the seal carrier. The thus prolonged annular gap between the seal carrier and the revolving bearing ring assumes the function of a labyrinth and thereby improves the sealing quality of the sealing arrangement.
According to another feature of the present invention, the sealing arrangement may include a sealing element which is received in the annular gap defined in radial direction by the seal carrier and the revolving bearing ring. Suitably, the sealing element is placed in the annular gap at a location distant to a securement zone of the seal carrier. The sealing element is suitably made of a material that deforms easily and does not affect the friction of the clutch release bearing to avoid a sliding contact and thus heating of the clutch release bearing also after the break-in phase.
When the seal carrier extends over the entire axial width of the revolving bearing ring, the free end of the seal carrier may be formed with a collar in the direction of the housing of the clutch release bearing. The provision of the collar prevents ingress of contaminants into an installation space which is defined radially by the housing of the clutch release bearing and the seal carrier and revolving bearing ring, respectively. In this way, the operation of the clutch release bearing is further enhanced.
According to another feature of the present invention, the free end of the revolving bearing ring may have a conical configuration so as to reduce the inner diameter of the revolving bearing ring. As a result, a wedge-shaped annular gap is established which is defined radially by the revolving bearing ring and the seal carrier. Contaminants or liquids migrating into the annular gap are conveyed back as soon as they reach the revolving bearing ring. The conical free end of the revolving bearing ring causes at the inner contour of the revolving bearing ring a decrease in circumferential speed. Dirt particles impinging on a revolving body shift always in the direction of greatest circumferential speed, so that the end portion of the revolving bearing ring, which acts as an inclined plane, causes a conveying effect and thereby prevents a further transport of contaminants or liquids into the sealing zone. Suitably, the inner contour of the revolving bearing ring may be provided with a conveying thread to further improve the sealing action of such a revolving bearing ring. The thread pattern is hereby suited to the rotation direction of the revolving bearing ring so that contaminants migrating to the conveying thread are forced to move in a direction away from the sealing zone.
According to another feature of the present invention, an intermediate space may be defined by the seal carrier and the revolving bearing ring in radial direction and the sealing element in axial direction, wherein the intermediate space is partially filled with lubricant. An example of lubricant includes grease with high adhesive property so as to reduce friction in the second sealing zone, i.e. between the sealing disc and revolving bearing ring which are in frictional contact. In addition, the introduction of adhesive grease in the intermediate space enhances the sealing effect of the sealing arrangement.
According to another feature of the present invention, the seal carrier may be provided with an annular groove which is open in the direction of the revolving bearing ring for receiving a sealing ring, e.g. a ring-shaped formed plastic part, or a felt ring, or a fleece ring. The sealing ring is urged against the revolving bearing ring at smallest possible contact pressure to define the first sealing zone of the sealing arrangement and assist in the effect of the sealing gap, respectively.
Suitably, the individual components of the sealing arrangement are made of different materials. The seal carrier may be produced on a large scale in the form of a deep-drawn part through a process without material removal. The sealing disc or sealing ring may be made in the form of a formed felt part or fleece part or as a component made of PA66GF. The use of a sealing disc of felt ensures the implementation of a smallest possible sealing gap between the sealing disc and the end surface of the revolving bearing ring after a break-in phase. This material ensures a good sealing action at minimal friction and is therefore preferably applicable as seal for a clutch release bearing.
According to another feature of the present invention, the seal carrier may be secured to the outer bearing ring in a force-fitting engagement, e.g. by providing the seal carrier on the outside with partially aligned retaining lugs of a diameter exceeding a diameter in a receiving zone of the outer bearing ring.